All cameras looking the same way despite being directed another way
The camera you refer to, isn't the active one. Press Ctrl+0 to set the selected camera in the viewport as 'active' or make it the actual scene camera under Properties > Scene > Camera, which is basically the same.

Tip: The triangle on top of the 'active camera' is filled up with a solid color.

Manual: https://docs.blender.org/manual/en/latest/editors/3dview/navigate/camera_view.html